by Laurent Lebreton
While the common misconception of global plastic pollution in our oceans is based on descriptions of the north Pacific gyre being a trash island the size of Texas, the reality is much more complicated.
Although plastic is not biodegradable unlike other floating marine debris, it is eventually broken down by the sunlight into microscopic particles that persist, are difficult to clean and may be eaten by small marine organisms, thus entering the food chain. In spite of the ocean currents accumulating marine debris into five identified gyres, the garbage patches vary in concentration and cannot be spotted on satellite images.
In order to get a better understanding of where the plastic particles are likely to be located and where they they might have originated, we have developed a computer model that tracks virtual particles that are released into the ocean based on coastal population, urban development and shipping traffic and transported using a global ocean circulation data archive. This way we are able to determine the various contributors to each accumulation zone – the five large oceanic gyres and also smaller marginal seas. With the study recently published in the Marine Pollution Bulletin, we developed an interactive visualisation to make the results also available to a broader audience in a graphic way allowing to explore plastic accumulation zones and concentrations around the globe and also to identify and compare its main contributors by regions.
As it is impossible to determine the exact amount of plastic pollution generated, the model considers the global pollution mass as unitary or 100% and determines how the global mass is relatively distributed. Further work will include a calibration with ocean based samples to validate the model and progress towards a more precise estimation of global plastic pollution in the marine environment.
By Laurent Lebreton, head of data science at data visualization creative agency Dumpark.